WO2012143078A9

WO2012143078A9 - Device for changing a compression ratio of a reciprocating piston internal combustion engine

Info

Publication number: WO2012143078A9
Application number: PCT/EP2012/001273
Authority: WO
Inventors: Ulrich Gutzer
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 2011-04-19
Filing date: 2012-03-22
Publication date: 2013-09-06
Also published as: US9249724B2; DE102011018166A1; EP2699779A1; US20140096748A1; WO2012143078A1

Abstract

A device for changing a compression ratio of a reciprocating piston internal combustion engine having a crank drive (1) with a crankshaft (2) with at least one crank pin (3) which is mounted in a rotationally movable fashion on both sides and is operatively connected to a connecting rod (4) and a piston (6) which is arranged in a sliding fashion in a cylinder (5) of the reciprocating piston internal combustion engine, in order to convert a rotational movement of the crankshaft (2) into a bidirectional, translatory movement of the piston (6) with a defined stroke height, wherein a rotationally movable, externally toothed eccentric (7) for changing the stroke height of the piston (6) is arranged between the crank pin (3) and a connecting eyelet on the connecting rod (4), wherein, in order to rotate the eccentric (7), an externally toothed, first gearwheel (8) is provided which is axially connected in a rotationally fixed fashion to a second gearwheel (9) via a shaft (10) which is arranged parallel to the crankshaft (2) which is arranged in a meshing fashion on a third gearwheel (12) which can be rotated by an actuating element (11), wherein the shaft (10) is arranged parallel to the crankshaft (2) and spaced radially apart therefrom.

Description

Device for changing a compression ratio of a reciprocating internal combustion engine

The invention relates to a device for changing a compression ratio of a reciprocating internal combustion engine having the features of the preamble of patent claim 1.

A variable compression ratio opens up consumption and performance potentials by adapting it to the load condition of the internal combustion engine, which remain unused with a fixed compression ratio.

Such an internal combustion engine is known for example from US Patent 1, 115.477.

Also known is the use of an eccentric bearing shell in the large connecting rod to represent a variable compression ratio or compression ratio, which rotates in the same direction at half crankshaft speed. The compression ratio is then adjustable by adjusting the phase angle of the bearing shell.

On the websites of Gomecsys, www.qomecsvs.com. is a generic device for changing the compression ratio- SES of a four-cylinder reciprocating internal combustion engine with a crank mechanism known. The crank mechanism has a crankshaft, with both sides rotatably mounted crank pin, which are in each case operatively connected to a connecting rod and a piston in a cylinder of the reciprocating internal combustion engine piston arranged displaceably. This results in the conversion of the rotational movement of the crankshaft into a bidirectional translational movement of the pistons in the cylinders with a defined lifting height. Between the crank pin and the connecting rod of the connecting rod in each case a rotatable, externally toothed eccentric is arranged, with the aid of which the lifting height of the piston adjustable, and the compression ratio is variable. Here, an externally toothed first gear is provided for rotating the eccentric, which is rotatably connected axially with a second gear via a shaft arranged parallel to the crankshaft. This gear interacts with an internally toothed gear which is twisted by a worm. By the rotation of the internally toothed gear thus the compression ratio of the reciprocating internal combustion engine is variable or adjustable.

A disadvantage of this configuration is a significant weakening of the load-bearing structure of the crankshaft, in particular in the region of the main bearing, by the necessary for Phasenwinkel-, or compression adjustment synchronization gear from the crankcase to the eccentric bearing shells. This leads to a reduction in the achievable increased efficiency of the internal combustion engine associated with the compression adjustment and to an increase in the frictional losses due to increased bearing diameters, whereby essential parts of the achievable potential are again consumed by the variable compression ratio of the internal combustion engine.

Object of the present invention is to avoid the above-mentioned disadvantages. This object is achieved by the feature in the characterizing part of patent claim 1.

It is inventively proposed a device (a synchronization gear) for changing the compression ratio of a reciprocating internal combustion engine, which acts around the lästtragenden crankshaft structures outside and at the same time ensures the necessary speed ratios. Here, the rotatably mounted in the crankcase gears (third and fourth gear) move only in the adjustment of the compression ratio, but not constantly due to the rotation of the crankshaft.

The proposed device according to claim 1 is suitable for a single-cylinder reciprocating internal combustion engine.

The embodiment according to claim 2 is a particularly preferred embodiment.

The embodiment according to claim 3 makes it possible to use the device according to the invention in multi-cylinder series reciprocating internal combustion engines.

The embodiment according to claim 4 is particularly compact.

The drives of the third or fourth gear according to claim 5 are particularly preferred embodiments.

The arrangement acc. Claim 6 is another preferred embodiment, with a direct action on the fifth gear is possible. The invention is explained in more detail below with reference to three exemplary embodiments in four figures.

Fig. 1 shows schematically a device according to the invention for

Changing a compression ratio for a reciprocating internal combustion engine with two cylinders.

Fig. 2 shows schematically a second device according to the invention for varying the compression ratio of a reciprocating internal combustion engine with six cylinders.

Fig. 3 shows schematically an end view of a device according to the invention

Device for changing the compression ratio of a reciprocating internal combustion engine for a first concrete embodiment.

Fig. 4 shows schematically an end view of a device according to the invention

Device for changing the compression ratio of a reciprocating internal combustion engine for a second concrete embodiment.

In the following, the same reference numbers apply to identical components in FIGS. 1 to 4.

Fig. 1 shows schematically a device according to the invention for varying a compression ratio of a reciprocating internal combustion engine with two cylinders.

The compression ratio ε is the ratio of an entire cylinder space of an internal combustion engine before compression to the remaining space after compression.

UK with

V _H = displacement (piston stroke * piston area) VK = compression volume

The reciprocating internal combustion engine has a crank mechanism 1, with a dashed crankshaft 2 with two mutually rotatably mounted crank pins 3, 3 ', each with a connecting rod 4, 4' and one in a cylinder 5, 5 'of the reciprocating internal combustion engine Bidirectionally sliding movably arranged pistons 6, 6 'are in operative connection. A crankshaft axis is numbered 2 '. This part of the device is used to convert a rotational movement of the crankshaft 2 in a bidirectional, translational movement of the piston 6, 6 'with a defined lifting height. Between the crank pins 3, 3 'and non-numbered connecting rods of the connecting rods 4, 4' is in each case a rotatable, externally toothed eccentric 7, 7 'arranged to change the lifting height of the piston 6, 6'. To rotate the eccentric 7, an externally toothed first gear 8 is provided, which is axially connected in rotation with a second gear via a parallel to the crankshaft 2 arranged wave 0. The second gear 9 is rotatably connected in this embodiment via the third gear 12 with a fourth gear 13 having a larger outer diameter than the revolving second gear 9. The fourth gear 13 is rotatably adjustable in this embodiment via an actuating element 11. The third and fourth gear 12, 13 are rotatably mounted in a crankcase of the reciprocating internal combustion engine. By adjusting the fourth gear 13, as already mentioned, the eccentric 7 is rotated and thus changes the compression ratio of the internal combustion engine. According to the invention, the shaft 10 is arranged parallel to and radially outwardly spaced from the crankshaft 2. This basic adjustment mechanism or this device for changing the compression ratio of the reciprocating internal combustion engine can be used for a reciprocating internal combustion engine with a cylinder.

However, since in the present embodiment, a reciprocating internal combustion engine is shown with two cylinders engages the outer teeth of the eccentric 7, a fifth gear 14, which rotatably connected via a parallel to the crankshaft axis 2 'arranged second shaft 15 rotatably connected to a sixth gear 14' , which transmits the adjustment movement of the fifth gear 14 to an outer toothing of the second eccentric 7 '.

In a further embodiment, the fourth gear 13 can be omitted and the actuator 11 acts directly on the third gear 12 a.

In the embodiment in Fig. 1, the second shaft 14 is disposed in an axial through hole of the crankshaft 2 coaxial with the crankshaft 2, which allows a very space-saving design. In other embodiments, the third or fourth gear 12, 3 may be rotated by the actuator 11 via a seventh gear or a rack or a worm or a slider.

Fig. 2 shows a device for varying the compression ratio of a reciprocating internal combustion engine with six cylinders. The two middle cylinders again show the same kinematics as FIG. 1, but adjacent to the two middle cylinders on each side there are two further non-numbered cylinders with the same crank mechanism, each having a drive through with a second shaft 15, for changing the Compression ratio of the four other, unnumbered cylinder. In the embodiment shown in FIG. 2, the cylinder 6 of the reciprocating internal combustion engine has a high compression 16 and the cylinder 6 'has a low compression 17.

Fig. 3 shows schematically an end view of the inventive device for varying the compression ratio of a reciprocating internal combustion engine for a specific embodiment, as can be used in Figures 1 and 2. In this real working embodiment, the gears have the following numbers of teeth:

Eccentric 7: 55 teeth

First gear 8: 15 teeth

Second gear 9 36 teeth

Third gear 12: 66 teeth

Fourth gear 13: 148 teeth

The directions of rotation of the individual gears to a larger compression ratio out are indicated schematically by arrows. The cylinder direction is upwards, d. H. in the direction of the crank pin, and the eccentric third

Fig. 4 shows schematically an end view of a device according to the invention for varying the compression ratio of a reciprocating internal combustion engine for a second specific embodiment. It essentially applies to Fig. 3 said, but in this second embodiment between the first gear 8 and the fifth gear 14, an intermediate gear 19 is arranged, which consists in this embodiment of only a single gear.

The directions of rotation of the individual gears to a larger compression ratio are again shown schematically by arrows. In other words, in summary:

It is thus proposed a Synchronisatipnsgetriebe which acts around the load-bearing crankshaft structures outside and ensures the necessary speed ratios. Here, the mounted in the crankcase gears 12, 13 move only during the adjustment of the compression ratio, but not constantly due to the rotation of the crankshaft 2. Between two cranks of the crankshaft synchronization takes place through the center of the Gruridlagerzapfens the crankshaft 2, as this often hollow, because at this point the crankshaft hardly a load is transmitted.

Thus, a system is proposed which generates no friction disadvantages by a larger crankshaft diameter.

With a suitable dimensioning of the plain bearings inside and outside on the eccentric bearing shell (width x diameter ³ are approximately the same inside and outside), these rotate by themselves with half the crankshaft speed, so that on average no drive energy is obtained. The sum of the friction of the two in each case crank pin connected in series sliding bearing can be even lower than that of an original Hubzapfenschleitlager from the prior art, namely, if the sum of the two bearing clearance can remain greater than that of the original one sliding bearing (the friction is proportional to the relative speed squared divided by the bearing clearance).

Since the position of the crankcase-side actuating element 11 clearly reflects the set compression ratio (in contrast to known systems, which have only one stop and the system can adjust itself under the acting forces), in the presence of a valve lift adjusting device (eg BMW Valvetronic) a mechanical coupling of valve lift or phase angle with the compression ratio. An example of the combination of a variable compression Ratio with a variable valve train is known for example from German Patent Application DE 10 2006 015 887 A1. Since low compression is generally combined with large valve lifts and vice versa at high load, valve releases in the piston can thus be minimized, which opens up further thermodynamic fuel consumption potentials through a more favorable combustion chamber shape.

Thus, according to the invention, consumption advantages for conventional reciprocating internal combustion engines with space-conforming technology are developed at very low adjustment energy. Further, maximum utilization of the potential of the variable compression ratio is achieved by direct, continuous and quick adjustability.

Bezuqszeicheniiste:

1. Crank drive

2. Crankshaft

2 'crankshaft axis

3. crankpin

3 'second crank pin

4. connecting rod

4 'second connecting rod

5th cylinder

5 'second cylinder

6. Piston

6 'second piston

7. eccentric

7 'second eccentric

8. first gear

9. second gear

10th wave ·

11th actuator

12. third gear

13th fourth gear

14th fifth gear

14 'sixth gear second wave

high compression low compression crankshaft main bearing intermediate gear

Claims

claims

1. A device for varying a compression ratio of a reciprocating internal combustion engine with a crank mechanism (1) with a crankshaft (2) with at least one both sides rotatably mounted crank pin (3) with a connecting rod (4) and one in a cylinder (5) Reciprocating internal combustion engine sliding movably arranged piston (6) is operatively connected, for converting a rotational movement of the crankshaft (2) in a bidirectional, translational, movement of the piston (6) with a defined lifting height, wherein between the crank pin (3) and a connecting rod of the connecting rod (4) a rotatable, externally toothed eccentric (7) is arranged to change the lifting height of the piston (6), wherein for rotation of the eccentric (7) an externally toothed first gear (8) is provided which axially with a second gear ( 9) via a crankshaft (2) parallel to the shaft (10) is rotatably connected, which rotatably on one of an adjusting element (11) Aren third gear (12) is arranged combing,

characterized in that the shaft (10) parallel and radially outwardly spaced from the crankshaft (2) is arranged.

Device according to claim 1,

characterized in that a fourth gear (13) is provided which is non-rotatably connected to the third gear (12), wherein the fourth gear (13) has a larger outer diameter than the third gear (12) and the fourth gear (13) of the adjusting element (11) is rotatable.

Device according to claim 1 or 2, wherein the crankshaft (2) has a second crankpin (3 ') which is connected to a second connecting rod (4') and a second piston (2) movably movably arranged in a second cylinder (5 ') of the reciprocating piston engine ( 6 ') is in operative connection, for converting the rotational movement of the crankshaft (2) in a bidirectional, translational movement of the second piston (6') with a defined lifting height, wherein between the second crank pin (3 ') and a second connecting rod eye of the second Pleuels (4 ') a rotatable externally toothed second eccentric (7') is arranged to change the lifting height of the second piston (6 '),

characterized in that for the rotation of the second eccentric (7 ') an externally toothed fifth gear (14) is provided, which is rotatably connected to a sixth gear (14') via a parallel to the crankshaft second shaft (15), wherein the sixth gear (13) with the externally toothed eccentric (7) is in operative connection.

Device according to claim 3,

characterized in that the second shaft (15) in an axial through hole of the crankshaft (2) is arranged coaxially with the crankshaft (2).

5. Device according to one of the claims 1 to 4,

characterized in that the third or the fourth gear (12, 13) of the adjusting element (11) via a seventh gear or a rack or a worm or a slider is rotatable.

6. Device according to one of the claims 1 to 5,

characterized in that between the first gear 8 and the fifth gear 14, an intermediate gear 19 is arranged.